In sewing machines of various types, threads are applied and manipulated on opposite sides of a fabric to form one or more series of stitches. The proper formation of the stitches of each series requires the cooperative movement and precise timing of cooperating stitching elements, including primarily a needle with which other elements must be synchronized. Improper timing or movement of a stitching element can result in improperly formed or inferior stitching, and in the malfunction or breaking of the thread, the stitching elements, or other elements of the machine.
Large scale automated quilting operations are performed on large commercial quilting machines. Such machines are, for example, disclosed in Gribetz et al. U.S. Pat. No. 5,154,130. Such quilting machines simultaneously sew a plurality of patterns on a multiple layered fabric using, as illustrated and described in the Gribetz et al. patent, a double lock chain stitch applied by each of a plurality of sets of stitching elements ganged in an array. The stitching elements in each of the sets employed in a double lock chain stitch quilting machine include a needle, which applies a top thread, and a looper, which applies a bottom thread. In addition, machines of the Gribetz type include, in each of the sets of stitching elements, a retainer that serves to guide the thread during a portion of each stitching cycle.
The needle and the looper in a chain stitch forming element set move cyclically through precisely timed and coordinated motions. In each cycle, the needle penetrates the fabric, drawing a top thread through the fabric, forming a top thread loop below the fabric that extends through the fabric, down through the eye of the needle, and back to the top of the fabric. At a precise point in the needle cycle, known in the art as the "loop take time", the tip of a looper, located below the fabric, moves along side of the needle, to insert a loop of the bottom thread through the top thread loop presented by the needle. The longitudinal and transverse positions of the path of the looper relative to the needle, as well as its timing relative to the motion of the needle, affect the ability of the elements to form the stitch, the quality of the stitch, and the life of the needle, looper and other machine components.
In automated quilting machines such as the Gribetz machine referred to above, banks or ganged arrays of needles form plural stitches simultaneously by operating in synchronized movements with similarly ganged arrays of loopers. In such machines, precise adjustment of every one of the sets of stitching elements must be maintained or any one of the stitched patterns could be defectively formed, resulting in the wasting of a large amount of fabric. Failure to maintain adjustment of any one of the sets of the array can also result in a failure of components of the machine, resulting in expensive repairs and costly loss in the productivity of expensive equipment.
In the past, multiple needle quilting machines have been initially adjusted by the machine manufacturer, with needles and loopers installed in one particular array to quilt products in one particular pattern. When pattern changes are required, the addition, movement, or removal of stitching elements of the array is performed by the equipment manufacturer's customer, the quilt manufacturer. When such changes are made to the array, the new needles and loopers that are installed must be precisely adjusted.
In addition, throughout the useful life of any array of stitching elements on a quilting machine, one or more elements may come out of adjustment, resulting in decline in the quality, or loss of, a stitched pattern, and the need to stop the machine and readjust the element involved. Typically, the vertical height of the needle is prone to become misadjusted, but usually the horizontal position of the needle in the array is fixed, barring the bending of a needle. Loopers, however, are usually adjustable in two or more directions relative to the needle, and thus are more prone to come out of adjustment. In addition, other elements such as needle guards on the loopers, retainer elements, thread cutting elements and other elements used in various machines can lose adjustment, requiring interruption of the use of the machine so that adjustment can be made.
In the past, stitching element adjustment, such as loop take time adjustment, in multiple needle quilting machines has involved the process of stopping the machine, manually moving a needle drive shaft, or a mechanically equivalent element, to an adjustment position, and then adjusting the position of at least one stitching element of a set, such as a looper relative to the needle, while holding the shaft in the proper adjustment position. In multiple needle quilting machines of the Gribetz type, such adjustments have been employed in the past by stopping the machine, manually rotating a needle drive shaft to align timing marks corresponding to the loop take time position of the needle, and then making element adjustments of the looper relative to the needle while the needle is in the loop take time position. Such adjustments are checked or made for any or all elements of an array.
In the making of stitching element adjustments, particularly the adjustment of looper position and timing relative to the needle in multiple needle quilting machines, the adjustment process has been time consuming. In addition, the step of manually positioning the needle drive to the precise loop take time position has resulted in the introduction of error that results in loss of quality in the adjustment being made or in prolonging the adjustment process as the operator rechecks and readjusts the settings. With large scale multiple needle quilting operations, there is a definite need for improved methods and devices that facilitate the stitching element adjustment process, particularly by speeding up and increasing the precision of the adjustment process.